I really like using tube calls, especially in the Fall. Kee-Kees and Kee-Kee runs work great on Fall birds and a tube is a great call to use.
I was able to call in a group of four longbeards by kee-keeing this Fall. One of those we ate for Thanksgiving.
Here is a Bocote tube I made recently.
This is my old Bloodwood tube that I use. Both of these have Acrylic mouthpieces. Some of my tubes have back Delrin mothpieces.